Centrifugal fan



July 1, 1958 J. R. DAVIS 2,841,326

CENTRIFUGAL FAN Filed June 14, 1954 4 2 Sheets-Sheet l INVENTOR. JA MESR. DAV/S ATTORNEYS J. R. DAVIS CENTRIFUGAL FAN July 1, 1958 2Sheets-Sheet 2 Filed June 14, 1954 INVENTOR. JAMES R. DAV/S ATTORNEYSUnited States Patent 1 2,841,326 CENTRIFUGAL FAN James R. Davis, LaCrosse, Wis., assignor to The Trane Company, La Crosse, Wis.

Application June 14, 1954, Serial No. 436,336 5 Claims. (Cl. 230-127)This invention relates to centrifugal fans wherein an impeller isrotatably mounted in a scroll shaped housing fordrawing air into the fanaxially thereof and discharging the air radially from the impeller intothe housing from which it flows through a discharge opening.

In order to provide a relatively large discharge opening, the sides ofthe fan housing are disposed at some distance from the sides of theimpeller and there is a tendency for the air to rotate continuously inthe housing, particularly about the inlet throat of the housing and theinlet side plate of the impeller. This rotation of air in the housingproduces losses which reduce the efficiency of the fan.

It is, therefore, an object of this invention to provide a first cut-offmember extending across said housing and a second cut-off memberextending from the side of the housing to a point adjacent to the outerperiphery of the side plate of the impeller.

It is a further object of the invention to provide a cu'Fo'If which willreduce recirculation of air about the inlet throat of the housing andthe inlet side plate of the impeller thus increasing the efiiciency ofthe fan.

It is still another object of the invention to provide a shroud in thehousing about the inlet thereof to reduce the recirculation of air inthe housing.

Further objects and advantages of this invention 'will become apparentas the specification proceeds to describe the invention with referenceto the accompanying drawof the fan of Figure 3.

The invention has been illustrated as applied to a centrifugal fanhaving an impeller positioned in a relatively large housing scroll topermit expansion of the air after passing through the impeller to obtaina low velocity discharge of air and the accompanying quiet operation.

The fan of this invention consists of a housing having parallel sidewalls 12 and 14 which are fastened to opposite edges of a scroll 16. Thehousing has a substantially rectangular discharge opening 18. Thedischarge opening 18 is spaced from and in a plane substantiallyparallel with a plane tangent to the periphery of the impeller 28. Twosides of the discharge opening are substantially at the housing sides 12and 14. A third side of the discharge opening is substantially at thescroll shaped wall 16. The fourth side of the discharge opening 18 issubstantially in a plane through the axis of rotation of the impeller 20and normal to the plane of the discharge opening 18.

An impeller 20 is positioned within the scroll housing 10 and is mountedon a drive shaft 22 which is rotatably supported in a bearing 24positioned externally of the scroll housing 10.

The impeller 26 has a plurality of blades 26 positioned about itsperiphery. The blades 26 extend between and are secured at their ends.to the inlet side plate 28 and the back side plate 30 of the impellerin any suitable manner as by welding or riveting.

, I The inlet side plate 28 of the impeller 20 has an inlet 2,841,325Patented July 1, 1958 opening 32 which forms the inlet plane of theimpeller. An inlet throat 34 is secured to the wall 12 in any suitablemanner as by welding, riveting, or bolting, and has the end 36 thereofextending within the inlet plane 32 of the impeller 20 to conduct airthrough the inlet throat and thence directly into the interior of theimpeller 20.

The side plate 12 of the housing 10 is formed inwardly to form a shroud38 surrounding inlet 34.

A main cut-oil member 4% extends across the discharge opening 18 and issecured at 42 to the scroll 16 in any suitable manner as by resistancewelding. In cross section the main cut-off .member 40 is substantiallyin the form of an inverted 'U.

A secondary cut-01f member 44 is secured to the main cut-oil member 40at 46 in any suitable manner as by resistance welding. Thesecondarycut-oflf member 44 extends from the side 12 of the housing to apoint short of the plane of the edge of the large end of the inlet sideplate 28 of the impeller 20.

It has been found that prior art fans having only a cut-off similar tothe main cut-oil 40 have permitted the air or gas to circulatecontinuously in the housing particularly about the inlet throat andabout the inlet side plate of the impeller.

This recirculation of air in the housing reduces the efficiency of thefan. In order to reduce this recirculation and increase the efficiencyof the fan, applicant has provided the shroud '38 and the secondarycut-01f member 44. The secondary cut-off member 44 provides etficientflow in the discharge area of the housing and prevents recirculationwith substan tial clearances between the impeller and stationary partsthus avoiding frictional losses which would otherwise result.

A fastening clip 50 is secured to the cut-ofi member 40 and to thehousing side plate 12 in any suitable manner as by resistance welding.Strut 48 is also secured to cut-off members 40 and 44 at 52 and 54respectively, in any suitable manner as by resistance welding. A strut56 is secured to members 40 and 44 at 58 and 60 respectively in anysuitable manner as by resistance welding.

The extremity of the second cut-oil member, as shown in the drawings, isrounded and is provided with portions 61 and 62, which are parallel tothe axis of rotation of the impeller.

In Figure 3 there is illustrated the use of the air cut-ofl members 40and 44 and the shroud 38 as applied to a double inlet centrifugal fan.The arrangement of the elements of construction of the double width fan10' is similar to that of the single width fan 10, however, since thereare two inlets there are two shrouds 38' and two secondary cut-offs 44.A single main cut-oil 40' extends entirely across the housing. Theshroud members 38' and secondary cut-ofl? members 44' function in thesame manner as described in connection with the operation of theapparatus illustrated in Figure 2.

The extremity of the second cut-01f member, as shown in the drawings, isrounded and is provided with portions 61 and 62, which are parallel tothe axis of rotation of the impeller.

While the apparatus disclosed and described herein constitutes apreferred form of the invention, yet it will be understood that theapparatus is capable of alteration without departing from the spirit ofthe invention, and that all modifications that fall within the scope ofthe appended claims are intended to be included herein.

Having thus fully described my invention, what I claim as new and desireto secure by Letters Patent is:

1. In a centrifugal fan, a housing of scroll form having spacedsubstantially parallel .sides and-a scroll shaped wall, an inlet throatextending within said housing from one side thereof, an impeller of thecentrifugal type having flow passages therein and having said flowpassages terminating, in a' peripheral air' discharge surface, means2,841,326. .r a uj r l rotatably mounting said impeller in said housingfor draw- 7 ing air through the inletu throat into said impeller anddischarging thesame from the fanhousing, a s'ubstan-V tially rectangulardischarge opening in saidhousing, said 7 opening being spaced from andin a plane substantially parallel with a plane tangent to" the periphery'of said impeller, two sides'ofsaid discharge opening beingsubstantially at the housing sides, a third side of said, dischargeopening being substantially at the scroll shaped wall, a'fourth side ofsaid discharge opening being sub- J stantially in a plane through theaxis of "rotation of the impeller and normal to the plane of saiddischarge opening, a first air cut-01f member secured to said housing atsaid fourth side of said discharge opening and extending ,into saiddischarge opening, said first air cut-off member being spaced fromandextending substantially across'said peripheral air discharge surfaceof said'impellen'and a second air cut-'oft' member, secured to saidhousing and extending from the inlet side of said housing substantiallyto said peripheral air'discharge surface of said impeller, said secondair cut-off member extending into the discharge opening from saidfourthside of said discharge opening a greater distance than said first aircut-E memcommunication with said inlet throat, said impeller havng"flow' passages therein'and having said' floW'passages terminating in aperipheral air discharge surface, means rotatably mounting said impellerin said' housing for' drawing air throughtsaid inlet throat into saidimpeller and discharging the samefrom the fan ho'using, a sub--stantially rectangulardischarge opening in said housing ofsubstantiallyrthe same'width as said housing, and an; 7

annular shroud member extending axially inwardly toward said impeller,said shroud'rnember being secured to said one side of said'housing andsurrounding said inlet throat, said annular shroud member being spacedfrom said inlet throat to reduce therecirculation of air arounds'aidinlet throat. a t r l 4. In a centrifugal fan, a housing of scrollingspaced substantially parallel sides and a scroll shaped her, saidimpeller having a side wall axially converging toward the said inletand'providing a passageway in the said side wall which registers withsaid inlet, the said 5;;

second cut-off member axially overlapping the said converging side wall.i

2. In a centrifugal fan, a housing of scroll form havingspaced'substantially parallel sides and a scroll shaped wall, an inletthroatextending within saidhousing from a one side thereof,-an impellerof the centrifugal type having flow passages formed by elements havingouter edges therein,'said flow passages terminating in a peripheral airdischarge surface, means rotatably mounting said im- V peller in. saidhousing for drawing air through the inlet throat into' said i'mpellerand discharging the same from the;fan housing, a substantiallyrectangular discharge openingin said housing, said opening being spacedfrom and in 'a plane substantially parallel with a plane tangent to theperiphery of said impeller, two sides of saiddischarge opening beingsubstantially at the housing sides, a thirdside of said dischargeopening being substantially at the scroll shaped wall, a fourth side ofsaid discharge opening being substantially in'a plane through the axisof rotation of the impeller and normal to the plane of said dischargeopening, a first air cut-off member secured tOsaidhousing at saidfourth'side of said discharge opening" and'extending into said dischargeopening, said first air cut-ofi 'rnember being spaced from and extendingsub- "stantially across said peripheral air discharge surface of to saidhousing and extending from the inlet side of said housing substantiallyto said peripheral air discharge surface of said impeller, said secondair cut-off member a said impeller, and a second air'cut-oif membersecured extending into the discharge opening from said fourth side ofsaid discharge opening a greater distance'than said first air cut-ofimember, said impeller having a side wall axially converging toward thesaid inlet and providing a "passageway in the said side wall whichregisters with said inlet, the said second cut-ofi' member axiallyoverlapping the said converging sidewall, the inner extremity of saidwall, an inlet throat extending within said? housing from each sidethereof, an impeller of the centrifugal type having inlet sideplates,each'of s aid side plates havingan air receiving opening incommunication with one of said inlet throats, said impeller having flowpassages therein and having said flow passages terminating in aperipheral air' discharge surface, means rotatably mounting saidimpeller in said housingfor drawing air throughsthe inlet throat intosaid impeller and discharging the same from said housing,a,substantially:rectangular discharge'open- 'ing in said housing, saidopeningbeing spaced from and a a in a plane substantially parallel witha plane tangent to the a periphery of said impeller, two of the sidesofsaid dis-- charge opening being substantially at thehousing sides, a

third side of said discharge opening being substantially at the scrollshaped wall, a fourth side of said discharge opening being substantiallyin a plane through the axis of rotation of the impeller and normal, tothe plane of said discharge opening, a first air cut-off member securedto said housing at said fourth side of said discharge opening andextending into said discharge opening, said firstair cut-01f memberbeing spaced from and extendinggsubstantially across said peripheral'air discharge surface of said impeller, additional air cut-off memberssecured to said housing and extending from the sides of said housingsubstantially to said peripheral, airdischarge surface of i saidimpeller, said additional air cut-ofi? members extending into saiddischarge opening from said fourth side of u said discharge opening agreater distance than said first air cut-off member, said impellerhaving a side wall axially converging toward the said inlet andproviding a passageway in the said side wall which registers with saidinlet, the said second cut-off member axially overlapping the saidconverging side wall.

5. In a centrifugal fan, a housing 'havingspaced substantially parallelsides and a scroll shaped Wall, an inlet throat extending within saidhousing from each side there- 7 of, an impeller of the centrifugal typehavinglinlet side 1 plates, each of said side plates having an airreceiving opening in communication with one of said inlet'throats,

said impeller having flow passages therein and having said How passagesterminating in a peripheral air discharge surface, a substantiallyrectangular discharge opening in said housing of substantially the samewidth as said housing, and annular shroud members extending axiallyinwardly toward said impeller, said shroud members being secured to thesides of said housing and surrounding said inlet throats, said annularshroud members being spaced from said inlet throats to reduce therecirculation of air 7 around said inlet throats.

References Cited in the file of this patentj UNITED STATES PATENTS2,107,897: McMahan Feb. 8, 1938 2,452,274 Walters oct. 26, 1943 7 VFOREIGN PATENTS 5,097 7 GreatBritain a of 1911 form hav-

